Replating is leaving your leftover food, in a doggie bag, on top of a trash can, so they don't go to waste. Check it out at replate.org, and try it out ... anywhere. I don't like wasting food, I do feel slightly unsure of this. A little research shows that this is at least going on in San Francisco, Philadelphia and Chicago. There is a discussion about it going on at chow.com, with some pointers for replating etiquette.
I originally heard about this through an episode of KCRW Good Food, the Raw Milk and Honey Episode.